Transmitting and receiving device for submarine sound waves



Dec, 23, 1924.

- W. HAHNEMANN TRANSMITTING AND macmvme DEVICE FOR SUBMARINE souun WAVESFiled March 24, 1921 Patented Dec. 23, 1924.

TATES ata FATE

FIRM SIGNAL GESELLSCI-IAFT M. B. IL, OF KIEL, GERMANY.

TRANSMITTING AND RECEIVING DEVICE FOR SUBMARINE SOUND WAVES.

Application filed March 2 1921.

To all whom it may concern:

Be it known that I, WALTER HAHNEMANN, citizen of the German Republic,residing at Kitzeberg, near Kiel, province of Schleswig- Holstein, Stateof Prussia, Germany, have invented certain new and useful Improvementsin and Relating to Transmitting and Receiving Devices for SubmarineSound Waves, of which the following is a specification.

In hydraulic submarine sound transmitting and receiving arrangements ofwhatever form of construction,such for example, as sirens, whistles, andhydraulic automatic interrupters,the production of sound in thesurrounding medium is based directly or indirectly upon the emanation ofa volume of liquid from a container under pressure, the liquid emanatingfrom the container into the surrounding water or into another containerwhich is in contact or in communication with the surrounding water. Insuch case the sound energy produced in the sur rounding water isdetermined by, or is at least dependent upon the quantity of wateremanating per period.

The transmitters and receivers heretofore known in the art and based onthe hydraulic principle have the disadvantage that the delivery of largequantities of water per period becomes impossible, because owing to theinconlpressibility of the liquid in the container imder pressure, a verygreat drop in pressure occurs in the container even when the volume ofthe liquid is only slightly reduced; thus a strong suction effect isproduced in the container which opposes the further emanation of liquidtherefrom. On the other hand, in the case of transmitters or receiversin which the emanated quantity of liquid is directed in turn into alimited volume of liquid, a very high counter-pressure is produced inthe latter even at the entry of less than the full quantity of theemanated liquid. Similar dificulties occur everywhere in submarine soundtransmitters or receivers operated hydraulically, in which severalliquid containers of limited size are employed.

Attempts have been made to remove these disadvantages by providing aircushions or the like in the containers (for instance, in the containersfrom which the sound producing quantities of water emanate or in SerialNo. 455,320.

containers which are connected with them), the air or the like in thesecushions serving as a compressible medium. These air cushions should,preferably be disposed at a distance of less than one-half the wavelength of the frequency used, from the point at which the soundproducing volume of water emanates or enters as the case may be.

The advantage of this arrangement, as compared with thepressure-equalizing tanks frequently used in hydraulic submarine sendersor receivers, resides in the fact that the sound pressure magnitudes aredirectly influenced at the point at which the sound is produced. If theair cushions were disposed further than one-half of a wave length from apoint of sound production, such as is the case in other well-knownarrangements, the production of the full pressure is already completedat the point of sound production before the pressure wave has reachedthe point at which it is cushioned by the compressible medium.

It has been found that in many cases the object aimed at, namely, anefficient control of the sound pressure field in regard to its pressuremagnitudes, is not sufficiently attained because the location of thecompressible medium with relation to the point of sound production is anunfavourable one. If, for instance, the buffer chambers filled withcompressible material are so arranged that they have only a smallsurface common with the radiation field to be controlled, or that theyhave only a small acting surface, then with a given oscillating massvery high velocities of those quantities of water which are to oscillateon the small surfaces of the buffer chambers must be produced. Suchaccelerations can hardly be obtained in practice.

A feature of the invention consists in so shaping the buffers that witha given volume they have a large surface.

In the accompanying drawing constructional examples of the invention areshown as applied to a submarine sound signalling device of the sirentype, in the interior of which device the sound pressure field is to bereduced. R indicates the rotor, S the stator, and LL the sound openingsof the siren. For cushioning the wave stroke in the interior of thesiren piston, air cushions KK are arranged, which, according to the Thespecific details of the flat air cushions or buffers are not ofimportance for the invention. They can, for example, be crinkled, asshown in Figure 3. It is only important that the arrangement should beas flat as possible and lamellar.

In principle, the invention is not limited to the use of gases as thecushioning medium. Instead of these, more or less solid or plasticmaterials of higher compressibility than water can be used, whichmaterials are brought into a flat extended form such as india rubbersheets or the like; also porous materials containingair, such asearthenware cells, can be used to advantage if they have a suflicientlyextensive surface; but homogeneous materials of high compressibility areto be preferred, because with these the active surface and the totalvolume can be calculated more exactly. Similarly the invention isnotlimited to any particular form of hydraulic sound signalling apparatus,but extends to all submarine sound apparatus in which butter orcushioning chambers are used for modifying the sound pressure field. Theinvention is particularly used with advantage where it is desired toproduce oscillations of relative large amplitude in the liquid bydireotexcitation with an electromagnet, without the necessity of employinglevers or special oscillatory structures in conjunction with thediaphragm.

Iclairnz I 7 ,LM'

1. A submarine sound communication plant, comprising in combination,sound communication apparatus, and a liquidpressure cushioning elementarranged in the communication apparatus, and a liquidpressure cushioningelement. arranged in the sound propagatinn liquid at a .pointfrorn saidapparatus not greater than one-half the wave length. of the sound wavesproduced. In testimony whereof I atfix my signa ture in presence of twowitnesses, i

1 VJ ALTER HAHNEMANN. 1 WVitnesses:

AENEAS MARKER,

EMIL Ltir'r.

submarine sound communication plant, comprising lD cCOIIIlOHIELtIOII,sound

